The invention is in the field of compositing methods and devices used to create composite images by combining a background scene and a foreground subject.
A blue screen composite-image process starts with a foreground subject in front of a blue or green backing. The process is most often called xe2x80x9cBlue Screenxe2x80x9d, or xe2x80x9cChroma Keyxe2x80x9d. The blue backing is replaced with a desired background scene as a result of a compositing process.
The incident lighting on the blue backing, which includes a blue floor, must be uniform because its level controls the observed level of the background scene in the composite image. The uniform lighting of the blue set includes uniform lighting of the foreground subject since the same lamps that light the backing generally illuminate the subject.
Illumination on the background scene may or may not be uniform. An example of non-uniform illumination is a background scene consisting of a room illuminated by a few overhead lamps. The light at the floor is therefore uneven with darker areas between lamps. The subject composited into such a background scene, when approaching an area close to an overhead lamp should show an increased illumination to provide a sense of realism, which it currently does not.
Foreground subjects composited against a computer-generated virtual background face the same problems as subjects composited against a background set constructed of plywood flats, wallpaper and paint. Lighting effects in the background have not been employed in either case. There has been no practical method for creating matched lighting effects for both background and foreground scenes that are being composited in real-time.
This invention automatically alters the apparent illumination level of the subject by varying the subjects RGB levels in a composite image when the subject appears to visit various areas in the background scene that have different illumination levels. When the subject enters such an area, the invented compositing device and methodology will automatically adjust the RGB levels of the foreground subject to a level that would have resulted if the scene had been real.